[LKP] Tips to append base tree info by git-format-patch

[Ye Xiaolong]

Hi,

Here's a tip for people who've been bothered by messages sent by kbuild bot like
below: 

[auto build test ERROR on net/master]
[also build test ERROR on v4.8-rc3 next-20160825]
[if your patch is applied to the wrong git tree, please drop us a note
to help improve the system]

It means that 0day bot applied the patch to net/master which is obtained based
on heuristic (0day bot does a guess job based on the MAINTAINERS file in linux
src to get the tree/branch ). It can't guarantee 100% accuracy. 

To avoid false reports which is caused by 0day apply your patches to a wrong
tree, we suggest to use the new option --base which is introduced since git
2.9.0 to append the base tree info, here is a example of it: 

Imagine that on top of the public commit P, you applied well-known
(on-flight) patches X, Y and Z from somebody else or yourself, and then built
your three-patch series A, B, C, the history would be like:

................................................
---P---X---Y---Z---A---B---C
................................................

With `git format-patch --base=P -3 C`, 

where P could be the exact commit sha, or variants e.g. HEAD~6, you can also use
--base=auto for convenience, the base tree information block is shown at the
end of the first message the command outputs (either the first patch, or the
cover letter), like this:

------------
base-commit: P
prerequisite-patch-id: X
prerequisite-patch-id: Y
prerequisite-patch-id: Z
------------

For more information, please refer to: https://git-scm.com/docs/git-format-patch

We'll be appreciated if you could use this option if you'd like your patch
series to be verified by 0day on a solid base as yours.

Feedbacks are welcome! Please drop us a mail if you have any suggestions.

Thanks,
Xiaolong